The AIDS Dementia Complex (ADC) is a frequent and important complication of AIDS in adults and children and a source of considerable morbidity and suffering. We propose to perform 18F- fluorodeoxyglucose (FDG)/positron emission tomographic (PET) scans in patients with-- or at high risk to develop-- ADC in order to (1) define the functional anatomy of ADC; (2) derive metabolic descriptors of disease severity and progression, which can be used to predict course and prognosis and, ultimately, to assess the effects of antiviral therapy; (3) study the effects of AZT and other anti-HIV drugs on cerebral glucose metabolism and (4) investigate the pathophysiology of the neuropsychiatric symptoms and signs of ADC and the nature and evolution of "subcortical dementia". A novel mathematical model of regional metabolic interactions, the Scaled Subprofile Model (SSM), and factor analysis of variance (FANOVA) will be employed to analyze PET region-of-interest (ROI) data and extract patterns of regional metabolic covariation as- sociated with disease severity and progression. This approach will provide an explicit method for quantifying the relationship between two correlational structures in PET/FOG data: (1) the covariation in rCMRGlu across ROI's and (2) rCMRGlu correlations with non- metabolic indices of disease severity (e.g., neuropsychological test scores).